1. Field of the Invention
The present invention relates to a manufacturing method of a voice coil bobbin for a speaker device.
2. Description of Related Art
It is known that a voice coil for a speaker device is formed by winding a wire around a voice coil bobbin (also simply referred to as “bobbin” hereinafter) of a film type or a pipe type (e.g., see Japanese Patent Applications Laid-open under No. 2002-300697, No. 8-205285 and No. 10-32897).
In addition, as a technique enabling high power input to a voice coil, there are known a technique of lapping a film material such as glassimide and polyimide film around the voice coil bobbin for plural times, and a technique of using a voice coil bobbin made of hard aluminum. Meanwhile, as the wire wound around the voice coil bobbin, a ceramic wire is known (see Japanese Patent Application Laid-open under No. 2002-222616, which is referred to as “Patent Reference-1” hereinafter).
In correspondence with recent improvement of heat resistance of a wire by the ceramic coating wire described in Patent Reference-1 and the like, high power input to the speaker device is significantly enhanced. Thereby, it happens that the wire falls from the bobbin at the time of the high power input operation and/or the bobbin is cut at a joint between the bobbin and the wire. Thus, it is necessary that the strength of the material of the bobbin is further enhanced in order to further improve high-power performance of the speaker device from now.